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The Quasi-Zenith Satellite System (QZSS) is a regional navigation satellite system commissioned by the Japanese Government as a National Space Development Program.


The Quasi-Zenith Satellite System (QZSS) is a regional navigation satellite system developed by [http://www.jaxa.jp JAXA] (Japanese version of NASA/ ESA), as a National Space Development Program for Japan.
==QZSS Introduction==


==QZSS Introduction==
[[File:Jaxalogo.PNG|Jaxa logo|thumb]]


QZSS was authorized by the Japanese government in 2002. In the beginning the system was started by the Advanced Space Business Corporation (ASBC) team, including Mitsubishi Electric Corp., Hitachi Ltd., and GNSS Technologies Inc. When in 2007 ASBC collapsed, the work was taken over by JAXA together with [http://www.eiseisokui.or.jp/en/ Satellite Positioning Research and Application Center (SPAC)], established in February 2007 and approved by the Ministers associated with QZSS research and development.


[[File:Jaxalogo.PNG|Jaxa logo|thumb]]
QZSS was authorized by the Japanese government in 2002. At the beginning the system was developed by the Advanced Space Business Corporation (ASBC) team,<ref name="SS">[http://www.aprsaf.org/data/aprsaf15_data/csawg/CSAWG_6d.pdf Shigeru Matsuoka, ''Service Status of QZSS'', Satellite Positioning Research and Application Center PNT Application and promotion Division, Dec.10 2008]</ref> including Mitsubishi Electric Corp., Hitachi Ltd., and GNSS Technologies Inc. When in 2007 ASBC collapsed, the work was taken over by JAXA together with [http://www.eiseisokui.or.jp/en/ Satellite Positioning Research and Application Center (SPAC)], established in February 2007 and approved by the Ministers associated with QZSS research and development.<ref name="QZSS_Wiki"/><ref name="QZSS_ICG">[http://www.unoosa.org/ ''Current Status of the Quasi-Zenith Satellite System''] Presentation at ICG-4 Meeting, Saint-Petersburg, September 2009</ref> In 2011, the Office of National Space Policy designated it to the top priority of Japan's space policy <ref name="ONSP_article">[https://global.jaxa.jp/article/special/michibiki/kunitomo_e.html ''The Office of National Space Policy and the Development of the Quasi-Zenith Satellite System''] Japan Aerospace Exploration Agency's article, 2003</ref>. In 2020, it still remained as one of the main keys to ensure Japanese space security <ref name = "Space_Plan">[https://www8.cao.go.jp/space/english/basicplan/2020/abstract_0825.pdf Outline of the Basic Plan on Space Policy] National Space Policy Secretariat, Cabinet Office, Government of Japan, 30 June 2020. </ref>.


==QZSS System description==
==QZSS System description==
[[File:Qzss-45-0_09.jpg|QZSS satellites groundtrack|thumb]]
The QZSS service area covers East Asia and Oceania region and its platform is multi-constellation GNSS. The QZSS system is not required to work in a stand-alone mode, but together with data from other GNSS satellites.<ref name="QZSS_Munich"/><ref name="QZSS_Wiki">[http://en.wikipedia.org/wiki/QZSS QZSS in Wikipedia]</ref>
The '''space segment''' consists of three satellites placed in periodic Highly Elliptical Orbit (HEO) and a fourth in a geo-stationary orbit.<ref name="QZSS_Wiki"/><ref name="QZSS_Munich"/> For the satellites in HEO, the perigee altitude is about 32000 km and apogee altitude about 40000 km, and all of them will pass over the same groundtrack so they are visible at all times from locations in the Asia-Oceania region. QZSS is designed so that at least one satellite out of three satellites exists near zenith over Japan. Given its orbit, each satellite appears almost overhead most of the time (i.e., more than 12 hours a day with an elevation above 70°). This gives rise to the term "quasi-zenith" for which the system is named. The design life of the quasi-zenith satellites is of 10 years. The first satellite ''Michibiki'' (QZS-1) was launched on 11 September 2010 and injected into the Quasi-Zenith Orbit on 27 September.<ref name="QZSS_ICG"/><ref name="QZSS_Munich"> Koji Terada (JAXA), ''Current Status of Quasi-Zenith Satellite System (QZSS), presentation at the Munich Navigation Congress, March 2011.</ref> In 2017 all three remaining satellites were launched: QZS-2 on 1 July 2017, QZS-4 on 9 October 2017 and the geostationary QZS-3 on 19 August 2017.
The '''ground segment''' is composed of a master control station (MCS), tracking control stations (TT&C), laser ranging stations and monitoring stations. The network of monitoring stations covers East Asia and Oceania region, with stations in Japan (Okinawa, Sarobetsu, Koganei, Ogasawara) and abroad: Bangalore (India), Guam, Canberra (Australia), Bangkok (Thailand) and Hawaii (USA).  The MSC is the responsible of the navigation message generation that are uplinked to the quasi-zenith satellite via a TT&C station place in Okinawa.<ref name="QZSS_ICG"/><ref name="QZSS_Munich"/>
The [[QZSS_Signal_Plan| '''signals''' planned and in operation]] for the QZSS system are:<ref name="QZSS_ICG"/><ref name = "Signals_web">[https://qzss.go.jp/en/overview/services/sv03_signals.html ''Transmission Signals'']</ref>
{| class="wikitable"
|-
! rowspan="4" | <br />Signal name
! <br />QSZ-1
! colspan="2" | <br />QSZ-2, QSZ-3 and QSZ-4
! rowspan="4" | <br />Transmission  service
! rowspan="4" | <br />Center  frequency
|-
! <br />Block IQ
! <br />Block IIQ
! <br />Block IIG
|-
! <br />Quasi zenith satellite orbit (QZO)
! <br />Quasi zenith satellite orbit (QZO)
! <br />Geostationary orbit (GEO)
|-
! <br />One satellite
! <br />Two satellites
! <br />One satellite
|-
| <br />L1C/A
| <br />◎
| <br />◎
| <br />◎
| <br />Satellite  Positioning, Navigation and Timing Service (PNT)
| rowspan="5" | <br />1575.42MHz
|-
| <br />L1C
| <br />◎
| <br />◎
| <br />◎
| <br />Satellite  Positioning, Navigation and Timing Service (PNT)
|-
| rowspan="2" | <br />L1S
| rowspan="2" | <br />◎
| rowspan="2" | <br />◎
| rowspan="2" | <br />◎
| <br />Sub-meter Level  Augmentation Service (SLAS)
|-
| <br />Satellite Report  for Disaster and Crisis Management (DC Report)
|-
| <br />L1Sb
| <br />-
| <br />-
| style="vertical-align:middle;" | <br />◎  Will be transmitted from around 2020
| style="vertical-align:middle;" | <br />SBAS Transmission Service
|- style="vertical-align:middle;"
| <br />L2C
| <br />◎
| <br />◎
| <br />◎
| <br />Satellite  Positioning, Navigation and Timing Service (PNT)
| <br />1227.60MHz
|-
| style="vertical-align:middle;" | <br />L5
| style="vertical-align:middle;" | <br />◎
| style="vertical-align:middle;" | <br />◎
| style="vertical-align:middle;" | <br />◎
| style="vertical-align:middle;" | <br />Satellite  Positioning, Navigation and Timing Service (PNT)
| rowspan="2" | <br />1176.45MHz
|-
| style="vertical-align:middle;" | <br />L5S
| style="vertical-align:middle;" | <br />-
| style="vertical-align:middle;" | <br />◎
| style="vertical-align:middle;" | <br />◎
| style="vertical-align:middle;" | <br />Positioning Technology Verification  Service
|- style="vertical-align:middle;"
| <br />L6 (LEX)
| <br />◎
| <br />◎
| <br />◎
| <br />Centimeter Level  Augmentation Service (CLAS)
| <br />1278.75MHz
|- style="vertical-align:middle;"
| <br />S-band
| <br />-
| <br />-
| <br />◎
| <br />QZSS Safety Confirmation Service
| <br />2GHz band
|}


The QZSS coverage area comprende East Asia and Oceania region and its platform is multi-constellation GNSS. In its specifications, QZSS system is not required to work in a stand-alone mode, but together with data from GNSS constellations.  
The multi-constellation GNSS interoperable signals, L1 C/A, L2C, L5 and L1C, are to be provided on the basis of no direct user fee. Compatibility is a mandatory requirement for QZSS system, working in the same frequency bands among the multi GNSS systems without harmful interference.  For the GPS performance enhancement signals, L1S and L6, a charging policy has been under examination. SPAC leads the investigation for L1S (sub meter class) and L6 (centimeter class) user terminals.<ref name="QZSS_ICG"/><ref name="QZSS_Munich"/>


The '''space segment''' consists of three satellites placed in periodic Highly Elliptical Orbit (HEO).  The Perigee Altitude is about 32000 km and Apogee altitude about 40000 km, and all of them will pass over the same groundtrack. QZSS is designed so that at least one satellite out of three satellites exists near zenith over Japan, meaning it appears almost overhead most of the time (i.e., more than 12 hours a day with an elevation above 70°). This gives rise to the term "quasi-zenith" for which the system is named. The design life of the quasi-zenith satellites is of 10 years. The first satellite 'Michibiki' was launched on 11 September 2010 and injected into the Quasi-Zenith Orbit on 27 September.
QZSS applications are: mobile mapping, IT aided precise farming, IT aided construction, fleet management, marine and transportation applications, among others. <ref name ="QZSS_Munich"/>


Image: Samegroundtrack
==QZSS Services==


The '''ground segment''' is composed of a master control station (MCS), a tracking control station (TT&C), laser ranging stations and monitoring stations. The network of monitoring stations covers East Asia and Oceania region, with stations in Canberra (Australia), Bangkok (Thailand) and Hawaii (USA). The MSC is the responsible of the navigation message generation that are uplinked to the quasi-zenith satellite via a TT&C station place in Okinawa.
All QZSS services are freely available to any user. However, the receivers and/or applications developed based on them may not receive signals or may receive incorrect signals due to no warranty of those <ref name = "PS-QZSS-002">[https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/ps-qzss-002.pdf?t=1623159964988 Quasi-Zenith Satellite System Performance Standard (PS-QZSS-002)] Cabinet Office, August, 20, 2020</ref><ref name="User_Report">[https://qbic-gnss.org/wp-content/uploads/2020/10/int-3-01.pdf QBIC Michibiki User Survey Report] 22nd May 2020 </ref>


There are 6 '''signals''' planned for the QZSS system shown in the next table:<ref>[http://qz-vision.jaxa.jp/USE/is-qzss/index_e.html QZSS system description in Jaxa website]</ref>
===Satellite Positioning, Navigation and Timing Service (PNT)===
This service can be used in an integrated way with GPS which translates in a higher number of visible satellites that allows for an improvement in the DOP. Moreover, the high elevation angles of the QZSS satellites allow for less multipath error. The system uses the same methods (double frequency, Klobuchar, etc.) to produce ionospheric correction parameters. QZSS produces two types of those parameters: ones for the Southeast Asia and Oceania, and others for Japan.


TABLAAAA
===Sub-meter Level Augmentation Service (SLAS)===
Sub-meter level augmentation data is transmitted in the L1S signals that are the same type as the L1C/A used in GPS. This service is intended for applications outside the mobile service range that are not heavily affected by time lags (pedestrians, bicycles, ships, etc.) as the augmentation information needs to be crafted before being sent and visibility of QZSS satellites can affect the service performance.


===Centimeter Level Augmentation Service (CLAS)===
[[File:CLASphases.png|Two-phase system installations for the overseas deployment of CLAS <ref name="Clas_Update"/>|thumb]]
Using data from the GNSS –based control stations of the Geospatial Information Authority of Japan, highly precise satellite positioning can be achieved. This information is transmitted by L6 signals that require dedicated receivers. This service is expected to be used in limited areas or in an auxiliary way as the augmentation information creation and transmission times may render immediate operation impossible.
The CLAS service started broadcasting a trial signal compliant with IS-QZSS-L6-003 using the L6D signal of QZS-3 the 1st of July 2020 and began its official broadcast of augmentation information in November 30 of 2020 <ref name="Clas_Update">[https://www.gpsworld.com/japans-clas-positioning-service-receives-major-upgrade/ Japan’s CLAS positioning service receives major upgrade] Tracy Cozzens, GPSWorld, December 2, 2020</ref><ref name="Clas_Expansion">[https://gnss.asia/blog/japan-clas-ews/ Japan’s plans to expand CLAS coverage and to launch Early Warning Service overseas] QZSS Business Innovation Council, GNSS Asia, 28, April, 2021</ref>.
This service has been evaluated and tested by 6 countries in the Asia-Pacific region since 2018. An ongoing overseas implementation of the service will provide wide area ionospheric correction data to regions with partnership agreements <ref name="Clas_Update"/>.


===Positioning Technology Verification Service===
QZSS satellites can be used by institutions to test their newly developed positioning technologies using L5S signals.
Satellite Report for Disaster and Crisis Management (DC Report)
This service uses the same L1S signals used by SLAS service and allows for transmission of crisis management information released by organizations for disaster prevention in intervals of four seconds. Powered street furniture and moving devices can be equipped with receivers to broadcast and display disaster-related information even in remote regions.
This service is currently being distributed in Japan but it is planned to be available for the Asia – Oceania region in 2024-2025 <ref name="Clas_Update"/>.


The multi-constellation GNSS interoperable signals, L1 C/A, L2C, L5 and L1C, are to be provided on the basis of no direct user fee. Compatibility is a mandatory requirement for QZSS system, working in the same frequency bands among the multi GNSS systems without harmful interference.  For the GPS performance enhancement signals, L1-SAIF and LEX, a charging policy is under examination. SPAC leads the investigation for L1-SAIF(sub meter class) and LEX(centimeter class) user terminals.
===QZSS Safety Confirmation Service (Q-ANPI)===
It has been proposed for this service to be used as an evacuation shelter data relay so that information about the location and opening of evacuation shelters, number of evacuees, and circumstances at evacuation shelters can be sent even with a damaged ground infrastructure. The system uses QZS and GEO satellites and is available on S-band devices that support Q-ANPI.


Compared to standalone GPS, the combined system GPS + QZSS will improve positioning performance via correction data provided through sub meter-class enhancement signals L1-SAIF and LEX. It will also improve reliability by means of failure monitoring and system health data notifications. The specification '''performances''' are:
===Public Regulated Service===
This service allows for positioning augmentation and time information acquisition via QZSS alone, even when GPS signal is jammed of spoofed. It is restricted to authorized users.


* The Signal-in-Space (SIS) User Range Error:  less than 1.6 m (95%), including time and coordination offset error.
===SBAS Transmission Service===
* Single Frequency User positioning accuracy (positioning accuracy combined GPS L1_C/A and QZSS L1_C/A):  21.9 m (95%).
Using the QZSS satellites placed on a GEO orbit, this service transmits the SBAS data crafted by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) that used to be transmitted from MTSAT.
* Dual Frequency User (L1-L2) positioning accuracy: 7.5 m (95%).
* L1-SAIF signal users (using WDGPS correction data) positioning accuracy: 1m (1 sigma rms) except in cases of large multipath error and large ionospheric disturbance.


For Single Frequency users the expected performances are three times better than the specified ones, i.e. 7.5m (95%).
==Performance==


QZSS '''applications''' are: mobile mapping, IT aided precise farming, IT aided construction, fleet management, marine and transportation applications, among others.
The specification performances are: <ref name="PS-QZSS-002"/>
 
* The Signal in Space (SIS) User Range Error: less than 2.6 m (95%).
* SLAS positioning accuracy: from under 2 m to under 1 m in the horizontal plane and from less than 2 m to less than 3 m in the vertical plane.
* CLAS positioning accuracy: less than 6 cm for horizontal and 12 cm for vertical (static).
 
The evaluated performances for 2020 were <ref name="Service_Performance">[https://sys.qzss.go.jp/dod/en/report/ Service Performance Evaluation]</ref>:
* The Signal in Space (SIS) User Range Error: between 0.52 and 1.10 m (95%).
* SLAS positioning accuracy: from 0.38 m to 0.84 m in the horizontal plane and from 0.55 m to 1.11 m in the vertical plane (95%).
* CLAS positioning accuracy: from 1.3 cm to 2.7 cm in the horizontal plane and from 3.7 cm to 6.3 cm in the vertical plane (95%).


==QZSS Development==
==QZSS Development==


The Initial Phase Operation started in September 2010 with the launch of the first quasi-zenith satellite, Michibiki , has been completed by summer 2011, with all functions of the satellite and the ground segment confirmed.  
The Initial Phase Operation that started in September 2010 with the launch of the first JAXA-operated quasi-zenith satellite, ''Michibiki'', was completed in 2011, with all functions of the satellite and the ground segment confirmed.<ref name="QZSS_Munich"/>
During the initial phase, technical verifications and applications demonstrations have been made using Michibiki. The demonstrations have shown that in a case of a car driving route inside Tokyo, time percentage when a GPS+QZSS user could get his position improve more than 10% of the GPS-only user, with a best improvement over 40% in the worst GPS DOP situation.
 
The next phase of the program will be the launch of the 2nd and 3rd QZSS satellites. This will be decided by the Strategic Headquarter for Space Policy of the Japanese government by the end of 2011.
During the initial phase, technical verifications and applications demonstrations were made using ''Michibiki''. The demonstrations showed that in a case of a car driving route inside Tokyo, time percentage when a GPS+QZSS user could get his position improved more than 10% of the GPS-only user, with a best improvement over 40% in the worst GPS DOP situation.<ref name="QZSS_Munich"/>
 
In 2011 the Government of Japan decided to accelerate the QZSS deployment in order to reach a 4-satellite constellation by the late 2010s, while aiming at a final 7-satellite constellation in the future<ref>[http://www.igs.org Future Plan of QZSS, 2012]</ref>.
 
Later on March 2013, the Japanese Cabinet Office formally announced a ¥50 billion (US$540 million) contract award with Mitsubishi to build one geostationary satellite and two additional quasi-zenith satellites (QZSs). That would complete the 4-satellite constellation by the end of 2017 that has been operated since November 2018 <ref name="Why">[https://qzss.go.jp/en/overview/services/sv02_why.html What is the Quasi-Zenith Satellite System (QZSS)?]</ref>. In addition, another contract was also signed with a special purpose company (led by NEC and supported by Mitsubishi UFJ Lease & Finance and Mitsubishi Electric Corporation) to fund the design and construction of the ground control system as well as its verification and maintenance for a period of 15 years <ref>[http://www.insidegnss.com Japan Awards Contracts for QZSS Space, Ground Segments, March 2013]</ref>.
 
Development and operation are conducted via a private finance initiative (PFI) project and Quasi-Zenith Satellite System Services Inc. (QSS) operates the four satellites, including QZS-1 <ref name="Why"/>.
The replacement of QZS-1, QZS-1R, was initially scheduled for mid-2020 but has been delayed to 2021 <ref name="Why"/><ref name="QZSS_Update>[https://www.enri.go.jp/~sakai/pub/gnss2018_sakai.pdf QZSS Update] ION GNSS+ 2018, September 26, 2018</ref>". The three new satellites to complete the 7-satellite constellation were scheduled to launch between 2022 and 2023 and have now all three been delayed further into 2023 <ref name="Why"/><ref name="QZSS_Update/>.
 
[[File:QZSS_Plans.gif|Constellation plans as of June 2021 <ref name="Why"/>|frame|center]]
 
This 7-satellite constellation will feature QZSS standalone PNT function with 1.0 meter (horizontal RMS error) for dual frequency code phase positioning, open service with Navigation Message Authentication (NMA), two-way ranging (ground-satellite) and inter satellite ranging to improve accuracy, availability and integrity, as well as PPP augmentation service and Disaster and Crisis management Report (DCR) for all the Asia-Pacific region. <ref name="ICG-14">[https://www.unoosa.org/documents/pdf/icg/2019/icg14/06.pdf The latest status of QuasiZenith Satellite System (QZSS) and its future expansion] ICG-14 Providers System and Service Updates, December 9, 2019, Bengaluru, India</ref>
 


==Notes==
==Notes==

Latest revision as of 11:53, 29 September 2021


QZSSQZSS
Title QZSS
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The Quasi-Zenith Satellite System (QZSS) is a regional navigation satellite system commissioned by the Japanese Government as a National Space Development Program.

QZSS Introduction

Jaxa logo


QZSS was authorized by the Japanese government in 2002. At the beginning the system was developed by the Advanced Space Business Corporation (ASBC) team,[1] including Mitsubishi Electric Corp., Hitachi Ltd., and GNSS Technologies Inc. When in 2007 ASBC collapsed, the work was taken over by JAXA together with Satellite Positioning Research and Application Center (SPAC), established in February 2007 and approved by the Ministers associated with QZSS research and development.[2][3] In 2011, the Office of National Space Policy designated it to the top priority of Japan's space policy [4]. In 2020, it still remained as one of the main keys to ensure Japanese space security [5].

QZSS System description

QZSS satellites groundtrack

The QZSS service area covers East Asia and Oceania region and its platform is multi-constellation GNSS. The QZSS system is not required to work in a stand-alone mode, but together with data from other GNSS satellites.[6][2]

The space segment consists of three satellites placed in periodic Highly Elliptical Orbit (HEO) and a fourth in a geo-stationary orbit.[2][6] For the satellites in HEO, the perigee altitude is about 32000 km and apogee altitude about 40000 km, and all of them will pass over the same groundtrack so they are visible at all times from locations in the Asia-Oceania region. QZSS is designed so that at least one satellite out of three satellites exists near zenith over Japan. Given its orbit, each satellite appears almost overhead most of the time (i.e., more than 12 hours a day with an elevation above 70°). This gives rise to the term "quasi-zenith" for which the system is named. The design life of the quasi-zenith satellites is of 10 years. The first satellite Michibiki (QZS-1) was launched on 11 September 2010 and injected into the Quasi-Zenith Orbit on 27 September.[3][6] In 2017 all three remaining satellites were launched: QZS-2 on 1 July 2017, QZS-4 on 9 October 2017 and the geostationary QZS-3 on 19 August 2017.

The ground segment is composed of a master control station (MCS), tracking control stations (TT&C), laser ranging stations and monitoring stations. The network of monitoring stations covers East Asia and Oceania region, with stations in Japan (Okinawa, Sarobetsu, Koganei, Ogasawara) and abroad: Bangalore (India), Guam, Canberra (Australia), Bangkok (Thailand) and Hawaii (USA). The MSC is the responsible of the navigation message generation that are uplinked to the quasi-zenith satellite via a TT&C station place in Okinawa.[3][6]

The signals planned and in operation for the QZSS system are:[3][7]


Signal name
QSZ-1
QSZ-2, QSZ-3 and QSZ-4
Transmission service
Center frequency

Block IQ
Block IIQ
Block IIG

Quasi zenith satellite orbit (QZO)
Quasi zenith satellite orbit (QZO)
Geostationary orbit (GEO)

One satellite
Two satellites
One satellite

L1C/A
◎
◎
◎
Satellite Positioning, Navigation and Timing Service (PNT)
1575.42MHz

L1C
◎
◎
◎
Satellite Positioning, Navigation and Timing Service (PNT)

L1S
◎
◎
◎
Sub-meter Level Augmentation Service (SLAS)

Satellite Report for Disaster and Crisis Management (DC Report)

L1Sb
-
-
◎ Will be transmitted from around 2020
SBAS Transmission Service

L2C
◎
◎
◎
Satellite Positioning, Navigation and Timing Service (PNT)
1227.60MHz

L5
◎
◎
◎
Satellite Positioning, Navigation and Timing Service (PNT)
1176.45MHz

L5S
-
◎
◎
Positioning Technology Verification Service

L6 (LEX)
◎
◎
◎
Centimeter Level Augmentation Service (CLAS)
1278.75MHz

S-band
-
-
◎
QZSS Safety Confirmation Service
2GHz band

The multi-constellation GNSS interoperable signals, L1 C/A, L2C, L5 and L1C, are to be provided on the basis of no direct user fee. Compatibility is a mandatory requirement for QZSS system, working in the same frequency bands among the multi GNSS systems without harmful interference. For the GPS performance enhancement signals, L1S and L6, a charging policy has been under examination. SPAC leads the investigation for L1S (sub meter class) and L6 (centimeter class) user terminals.[3][6]

QZSS applications are: mobile mapping, IT aided precise farming, IT aided construction, fleet management, marine and transportation applications, among others. [6]

QZSS Services

All QZSS services are freely available to any user. However, the receivers and/or applications developed based on them may not receive signals or may receive incorrect signals due to no warranty of those [8][9]

Satellite Positioning, Navigation and Timing Service (PNT)

This service can be used in an integrated way with GPS which translates in a higher number of visible satellites that allows for an improvement in the DOP. Moreover, the high elevation angles of the QZSS satellites allow for less multipath error. The system uses the same methods (double frequency, Klobuchar, etc.) to produce ionospheric correction parameters. QZSS produces two types of those parameters: ones for the Southeast Asia and Oceania, and others for Japan.

Sub-meter Level Augmentation Service (SLAS)

Sub-meter level augmentation data is transmitted in the L1S signals that are the same type as the L1C/A used in GPS. This service is intended for applications outside the mobile service range that are not heavily affected by time lags (pedestrians, bicycles, ships, etc.) as the augmentation information needs to be crafted before being sent and visibility of QZSS satellites can affect the service performance.

Centimeter Level Augmentation Service (CLAS)

Two-phase system installations for the overseas deployment of CLAS [10]

Using data from the GNSS –based control stations of the Geospatial Information Authority of Japan, highly precise satellite positioning can be achieved. This information is transmitted by L6 signals that require dedicated receivers. This service is expected to be used in limited areas or in an auxiliary way as the augmentation information creation and transmission times may render immediate operation impossible. The CLAS service started broadcasting a trial signal compliant with IS-QZSS-L6-003 using the L6D signal of QZS-3 the 1st of July 2020 and began its official broadcast of augmentation information in November 30 of 2020 [10][11]. This service has been evaluated and tested by 6 countries in the Asia-Pacific region since 2018. An ongoing overseas implementation of the service will provide wide area ionospheric correction data to regions with partnership agreements [10].

Positioning Technology Verification Service

QZSS satellites can be used by institutions to test their newly developed positioning technologies using L5S signals. Satellite Report for Disaster and Crisis Management (DC Report) This service uses the same L1S signals used by SLAS service and allows for transmission of crisis management information released by organizations for disaster prevention in intervals of four seconds. Powered street furniture and moving devices can be equipped with receivers to broadcast and display disaster-related information even in remote regions. This service is currently being distributed in Japan but it is planned to be available for the Asia – Oceania region in 2024-2025 [10].

QZSS Safety Confirmation Service (Q-ANPI)

It has been proposed for this service to be used as an evacuation shelter data relay so that information about the location and opening of evacuation shelters, number of evacuees, and circumstances at evacuation shelters can be sent even with a damaged ground infrastructure. The system uses QZS and GEO satellites and is available on S-band devices that support Q-ANPI.

Public Regulated Service

This service allows for positioning augmentation and time information acquisition via QZSS alone, even when GPS signal is jammed of spoofed. It is restricted to authorized users.

SBAS Transmission Service

Using the QZSS satellites placed on a GEO orbit, this service transmits the SBAS data crafted by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) that used to be transmitted from MTSAT.

Performance

The specification performances are: [8]

  • The Signal in Space (SIS) User Range Error: less than 2.6 m (95%).
  • SLAS positioning accuracy: from under 2 m to under 1 m in the horizontal plane and from less than 2 m to less than 3 m in the vertical plane.
  • CLAS positioning accuracy: less than 6 cm for horizontal and 12 cm for vertical (static).

The evaluated performances for 2020 were [12]:

  • The Signal in Space (SIS) User Range Error: between 0.52 and 1.10 m (95%).
  • SLAS positioning accuracy: from 0.38 m to 0.84 m in the horizontal plane and from 0.55 m to 1.11 m in the vertical plane (95%).
  • CLAS positioning accuracy: from 1.3 cm to 2.7 cm in the horizontal plane and from 3.7 cm to 6.3 cm in the vertical plane (95%).

QZSS Development

The Initial Phase Operation that started in September 2010 with the launch of the first JAXA-operated quasi-zenith satellite, Michibiki, was completed in 2011, with all functions of the satellite and the ground segment confirmed.[6]

During the initial phase, technical verifications and applications demonstrations were made using Michibiki. The demonstrations showed that in a case of a car driving route inside Tokyo, time percentage when a GPS+QZSS user could get his position improved more than 10% of the GPS-only user, with a best improvement over 40% in the worst GPS DOP situation.[6]

In 2011 the Government of Japan decided to accelerate the QZSS deployment in order to reach a 4-satellite constellation by the late 2010s, while aiming at a final 7-satellite constellation in the future[13].

Later on March 2013, the Japanese Cabinet Office formally announced a ¥50 billion (US$540 million) contract award with Mitsubishi to build one geostationary satellite and two additional quasi-zenith satellites (QZSs). That would complete the 4-satellite constellation by the end of 2017 that has been operated since November 2018 [14]. In addition, another contract was also signed with a special purpose company (led by NEC and supported by Mitsubishi UFJ Lease & Finance and Mitsubishi Electric Corporation) to fund the design and construction of the ground control system as well as its verification and maintenance for a period of 15 years [15].

Development and operation are conducted via a private finance initiative (PFI) project and Quasi-Zenith Satellite System Services Inc. (QSS) operates the four satellites, including QZS-1 [14]. The replacement of QZS-1, QZS-1R, was initially scheduled for mid-2020 but has been delayed to 2021 [14][16]". The three new satellites to complete the 7-satellite constellation were scheduled to launch between 2022 and 2023 and have now all three been delayed further into 2023 [14][16].

Constellation plans as of June 2021 [14]

This 7-satellite constellation will feature QZSS standalone PNT function with 1.0 meter (horizontal RMS error) for dual frequency code phase positioning, open service with Navigation Message Authentication (NMA), two-way ranging (ground-satellite) and inter satellite ranging to improve accuracy, availability and integrity, as well as PPP augmentation service and Disaster and Crisis management Report (DCR) for all the Asia-Pacific region. [17]


Notes


References

  1. ^ Shigeru Matsuoka, Service Status of QZSS, Satellite Positioning Research and Application Center PNT Application and promotion Division, Dec.10 2008
  2. ^ a b c QZSS in Wikipedia
  3. ^ a b c d e Current Status of the Quasi-Zenith Satellite System Presentation at ICG-4 Meeting, Saint-Petersburg, September 2009
  4. ^ The Office of National Space Policy and the Development of the Quasi-Zenith Satellite System Japan Aerospace Exploration Agency's article, 2003
  5. ^ Outline of the Basic Plan on Space Policy National Space Policy Secretariat, Cabinet Office, Government of Japan, 30 June 2020.
  6. ^ a b c d e f g h Koji Terada (JAXA), Current Status of Quasi-Zenith Satellite System (QZSS), presentation at the Munich Navigation Congress, March 2011.
  7. ^ Transmission Signals
  8. ^ a b Quasi-Zenith Satellite System Performance Standard (PS-QZSS-002) Cabinet Office, August, 20, 2020
  9. ^ QBIC Michibiki User Survey Report 22nd May 2020
  10. ^ a b c d Japan’s CLAS positioning service receives major upgrade Tracy Cozzens, GPSWorld, December 2, 2020
  11. ^ Japan’s plans to expand CLAS coverage and to launch Early Warning Service overseas QZSS Business Innovation Council, GNSS Asia, 28, April, 2021
  12. ^ Service Performance Evaluation
  13. ^ Future Plan of QZSS, 2012
  14. ^ a b c d e What is the Quasi-Zenith Satellite System (QZSS)?
  15. ^ Japan Awards Contracts for QZSS Space, Ground Segments, March 2013
  16. ^ a b QZSS Update ION GNSS+ 2018, September 26, 2018
  17. ^ The latest status of QuasiZenith Satellite System (QZSS) and its future expansion ICG-14 Providers System and Service Updates, December 9, 2019, Bengaluru, India
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